Allele Inheritance

Everyone has two alleles at each SNP. You get one allele from your mom and the other from your dad.

The major and minor alleles exist in one of three possible combinations in each person. Geneticists call these genotypes. Genotypes include:

• Homozygous major (two copies of the major allele)
• Homozygous minor (two copies of the minor allele)
• Heterozygous (one copy of each)

For example, two alleles of the BDNF gene are the major ‘C’ and the minor ‘T’. The possible genotype combinations are:

• ‘CC’ (homozygous major)
• ‘CT’ (heterozygous)
• ‘TT’ (homozygous minor)